If you are giving up something because it is bad for you and you would rather not do it, I think it is silly to need an outside reason to do so, have some self-control. If you are just giving up something for the sake of giving it up in some sort of sacrificial sense, why bother?
Fun fact: In 2nd grade, 8manpick was outed by a couple girls in his class as not very religious when he had no idea what they were talking about when they asked what he had given up for Lent.